Modern wind turbines comprise a plurality of wind turbine rotor blades, typically three rotor blades, each blade today having a weight of up to 13 tons and a length of up to 49 meters. At one end the rotor blade is to be attached to the wind turbine hub today up to 125 meters above the ground. This end has a diameter typically about 1-4 meters, and often it comprises about 90 bolts to be fixed at the hub in order to fix the rotor blade hereto.
Usually, wind turbines are erected in places in which the wind conditions are advantageous, e.g. at places with few obstacles blocking or altering the path of the wind. Consequently, wind turbines are often erected in more or less remote places, typically with a poor infrastructure in terms of road quality. Furthermore, wind turbine sites may be scattered over many square meters. The wind turbines may also be erected off-shore, where the wind conditions likewise may be advantageous.
The positioning at remote places and/or the size of the wind turbine sites may cause problems in relation to the necessary maintenance of the wind turbine components, e.g. the wind turbine rotor blades. These problems have recently increased due to the increasing size of the wind turbines.
As an example, wind turbine generators and wind turbine towers can be struck by lighting that can damage the generator or wind turbine rotor blades, thus necessitating repair or replacement hereof or parts hereof.
Previously, large mobile cranes have been used in connection with maintenance, repair, and exchange of wind turbine components. However, with a poor infrastructure and/or a considerable size of the wind turbine sites, the transportation of a crane to the wind turbine site can be both costly and time consuming.